The present invention relates to resin impregnation of absorbent lining materials to be used in the repair of damaged underground pipes and passageway walls, and relates particularly to insuring that curable resin material is thoroughly and efficiently distributed in such absorbent lining materials.
Damaged pipes, particularly large underground pipes, can be repaired by installation of reinforcing linings much more quickly and at much lesser expense than by removing and replacing the pipes, especially where such pipes are located beneath city streets and buildings. Even though such linings within repaired pipes will slightly reduce the interior volume of the repaired pipes, the interior surfaces of such linings are smoother than those of old cracked or corroded pipe walls and the flow capacity of repaired pipes often is greater than the capacity of the original pipes before such repair.
The process of installing a liner including an absorbent layer and a layer of a resin-impermeable film to repair pipes and passageways is explained in general terms in Wood, U.S. Pat. No. 4,366,012. Typically, a fibrous, absorbent layer of a tubular liner is impregnated with curable resin material under conditions in which the resin does not begin to cure, and curing is initiated only after the liner has been installed in the pipe being repaired. Once the impregnation of the absorbent portion of the liner with a resin has been accomplished, however, it is difficult or impossible to detect and correct inadequately impregnated portions of the liner material. Thus, it is very important not to leave air in the absorbent material of a liner where such air might remain and prevent the resin from permeating the liner material.
The manner of impregnating an absorbent portion of a liner with a curable resin material as taught in the Wood patent, however, suffers from serious shortcomings, particularly with respect to liners for pipes such as large sewer conduits. Wood teaches the resin-impregnation of the absorbent layer of a liner being prepared for installation by forming a hole in the impermeable film and applying a cup to the film, and then applying a vacuum to the liner through the cup. A first portion of the liner is evacuated in that way, and curable resin is then forced into the absorbent material of that portion of the liner by a mechanism such as a pair of rollers applying pressure to the liner to move a quantity of resin through the interior of the liner along its length. A further portion of the liner is evacuated, in turn, by moving the suction cup to another hole in the film.
Such a progressive evacuation is undesirably time-consuming, and such a cup is not particularly reliable in maintaining a tight seal to create a vacuum within a tubular liner being prepared for installation.
It is also known to use one or more hollow tubular needles, inserted through the resin-impermeable layer of a tubular liner as a pathway for removal of air from the interior of the liner so that its absorbent layer can be impregnated with a curable resin, as taught in Catallo, et al., U.S. Pat. No. 5,699,838. In a multiple-needle process of evacuating such a tubular liner in order to impregnate its absorbent portions a small number of such needles are used serially to puncture the resin-impermeable film and evacuate air from an absorbent layer of only a portion of a liner tube closely ahead of a quantity of curable resin being moved along and urged into the absorbent wall material of the liner.
Everson, et al., U.S. Pat. No. 4,182,262 describes a process which is probably even less efficient in evacuating the liner to promote absorption of a curable resin material, since a vacuum is applied only at an opposite end of a tubular liner from the location where resin material is introduced.
All of the known prior art methods thus provide only time consuming and inefficient evacuation and resin impregnation of the absorbent material of a liner for use in repair of a pipe, as such methods have been used to evacuate the absorbent material of a liner tube only during the process of installation of resin in the absorbent material of the liner. What is needed, then, is an improved method, and apparatus for use in accordance with such a method, for efficiently evacuating and impregnating a tubular liner with curable resin to prepare such a liner to be installed to repair damaged or deteriorated pipes and conduits.